Question 1
Cooking an egg is one type of process, while the formation of snow is another. In three to five sentences, identify each as exothermic or endothermic and explain how you know.
Question 2
Group 1 elements have an average electronegativity of 0.84 (not including hydrogen). Group 17 elements have an average electronegativity of 2.99. These two groups often form bonds. Given this information, which kind of bond will they likely form (ionic or covalent), and what evidence supports your claim? If it is ionic, then include which group gives up its electron to the other group. In three to five sentences, explain your reasoning.
Question 2
Use the table to answer the question:
Bond
Bond Energy
H-H
432
Cl-Cl
239
H-Cl
427
Explain how you would calculate the total change in bond energy for the reaction H2 + Cl2 -> 2HCl. How would you know if the reaction was endothermic or exothermic?
Question 1: Cooking an egg is an exothermic process because energy is released in the form of heat. This can be observed by the fact that when an egg is heated, it cooks and becomes solid, indicating a release of energy. On the other hand, the formation of snow is an endothermic process because energy is absorbed from the surroundings. Snow is formed when water vapor in the air freezes to form ice crystals, which requires energy to be taken in from the environment.
Question 2: Given that Group 1 elements have a low electronegativity and Group 17 elements have a high electronegativity, it is likely that they will form an ionic bond. Ionic bonds occur between elements with significantly different electronegativities, where one atom tends to give up electrons to the other. In this case, the Group 1 elements (with low electronegativity) would likely give up their electrons to the Group 17 elements (with high electronegativity) to form an ionic bond.
Question 3: The total change in bond energy for the reaction H2 + Cl2 -> 2HCl can be calculated by summing up the bond energies of the individual bonds broken and formed. In this case, the bond energy of two H-H bonds in H2 is 432 kJ/mol, the bond energy of one Cl-Cl bond is 239 kJ/mol, and the bond energy of two H-Cl bonds in 2HCl is 427 kJ/mol. Therefore, the total change in bond energy would be (2 * 432 kJ/mol) + (1 * 239 kJ/mol) - (2 * 427 kJ/mol) = -269 kJ/mol.
To determine if the reaction is endothermic or exothermic, we look at the sign of the total change in bond energy. If the value is negative, as in this case (-269 kJ/mol), it indicates that more energy was released during the formation of the products (HCl) than was consumed during the breaking of the reactants (H2 and Cl2). Therefore, the reaction is exothermic.